1. Field of the Invention
The present invention relates to a method and apparatus for the manufacture of non-woven textile fabrics.
2. Description of the Prior Art
Non-woven textile fabrics are well-known articles and essentially comprise longitudinal warp yarns and transverse weft yarns, it being possible for the weft yarns to be either perpendicular to the warp yarns or inclined to the latter, the cohesion of the whole being effected by glueing the yarns to one another at their points of intersection.
Numerous techniques are used for producing these articles.
Thus, French Pat. No. 501,934 describes the production of a textile fabric which is capable of being incorporated between two sheets of paper, the fabric being obtained by winding a series of yarns in a helix around the two selvedge yarns, which series of yarns are fed from bobbins assembled on endless chains or conveyors circulating continuously around the selvedge yarns. The selvedge yarns can optionally be taken from bobbins arranged outside the apparatus, and can pass inside the path of the bobbins and yarn-guides through hollow spindles.
Such a device makes it possible to obtain fabrics in which the yarns cross one another to form diamond shapes.
French Pat. No. 539,822 describes an apparatus for obtaining a network of warp and weft yarns which cross each other approximately at right-angles. According to this document, the weft web is obtained by wrapping a plurality of weft yarns around two laterally spaced, substantially parallel helical yarn guide members, the yarns being wrapped in successive turns of the helices of yarn guide members, which are rotated so that the weft yarns are advanced. The weft yarns are fed from bobbins assembled on a rotary unit, from which they unwind normally around the two helical yarn guide members, the wrapping being achieved by means of rotary arms which lay down their yarn between the turns of the turns of the helices. In order to increase their output, it is possible to use helical yarn guide members comprising a plurality of individual helices which are imbricated with one another. the number of these helices being equal to the number of bobbins to be unwound.
Preferably, each helix respectively comprises one or more rods, which advantageously have a round cross-section, the diameter of the rods being approximately equal to the distance which should exist between two weft yarns.
The weft web formed is combined with a warp web, it being possible for this warp web to be incorporated either inside the weft web or superimposed on the latter.
Such an apparatus is generally satisfactory; however, it exhibits the disadvantage of having a relatively limited production speed, because the bobbins which feed the weft yarns are arranged at the periphery of the rotary element which supports them and become further from the axis of rotation of this support as the width of the web formed increases. Furthermore, in accordance with the method of production described in this document, the weft yarn bobbins are relatively difficult to change.
Finally, as the helices rotate at the same speed as the rotary arms, the weft yarns cross one another in the middle of the web formed.
Numerous other documents describe improvements in this technique which make it possible, in particular, to produce, according to this process, weft webs in which the yarns are rigorously parallel to one another.
Thus, French Pat. No. 1,524,992 and U.S. Pat. No. 3,422,511 describe a method according to which two weft yarns are dispensed around helical yarn guide members comprising two intertwined helices, the yarns being arranged in a parallel manner by dispensing the yarns with a displacement of a quarter of a pitch between the turns of the helices, for example, by using a rotary component having four hollow arms which are angularly displaced by 90.degree., the yarn being dispensed by two adjacent arms which are 90.degree. apart, whereby the other two arms do not dispense any yarn and are only used for dynamic balancing of the unit.
Such a method has the disadvantage of only dispensing yarns over half the rotation of the dispensing component, which substantially reduces the output.
Furthermore, if the helices rotate at the same speed as the dispensing arms, parallel yarns are indeed obtained but, with this process, it is impossible to dispense more than two yarns per rotation of the dispensing element.
French Pat. No. 2,067,607 and U.S. Pat. No. 3,643,300 describe a device which also makes it possible to produce non-woven textile fabrics from a rotating element for dispensing two weft around two selvedge yarns and/or warp yarns, one of the two bobbins being fixed inside and the other being fixed outside the volume delimited by the rotation of the rotating element.
According to this document, the two weft yarns are also dispensed around rotary lateral elements in the form of a helix. When it is desired that the weft yarns should be parallel to one another, it is necessary to use helices which have a different structure from each other and also rotate at different speeds. Thus, on the one hand, one of the helices must be a single helix having a pitch which is double that of the weft web being obtained and rotating at a speed which is double the speed of rotation of the dispensing element and, on the other hand, the other helix must be a double helix which comprises two helices and rotates at the same speed as the dispensing element, these helices having a pitch which is four times that of the weft web and being mounted one inside the other.
Such a device is therefore complex and only makes it possible to dispense two weft yarns. Furthermore, the selvedges of the article formed are not symmetrical, which is disadvantageous when the fabric is used.
Admittedly, such a device exhibits the advantage that it avoids the necessity of moving the weft bobbins, but it has limited efficiency since, for each rotation of the rotating element, only two weft yarns can be dispensed. Furthermore, the helical yarn guide members, around which the weft yarns are arranged, are mounted at the ends of an arm which must be immobilized by means of stops, in order to prevent it from being caused to rotate. This immobilisation is generally achieved by means of a simple wedge placed below the helices. Such an assembly therefore creates numerous vibrations and makes it difficult to position the weft yarns precisely.
Finally, French Pat. Nos. 1,367,567, 1,537,811 and 2,118,877 also describe various techniques to produce nonwoven textile fabrics comprising transverse yarns.